Humans lived as hunter-gatherers for the vast majority of their evolutionaryhistory (the genus Homo has existed for about 2 million years). Agriculture originated only 10,000 years ago and has been practiced by the majority of the world's population for just two or three millennia, a relatively brief period of time for selection to act. Anatomically modern humans evolved some 150,000-200,000 years ago. This means that natural selection on age profiles of physical function, morbidity and mortality hazards occurred largely in the context of a foraging lifestyle. Yet, very little is known about the aging process among hunting and gathering peoples. The proposed research has three broad aims. The first is to conduct an integrated study of physical growth, development, aging, health and mortality in one population, the Tsimane', a forager-horticultural society with little market involvement and access to modern health care. The second aim is to advance theory in the biodemography ofthe human life course, with a specific focus on aging and lifespan. The third is to lay the groundwork for collaborative, comparative research in human aging across a diverse array of ecological and social settings. The long-term goal of the research is to explain the age profile of human mortality and the rate at which humans develop and senesce in terms of economic productivity, muscular strength, endurance, body composition, disease resistance, and cognitive function. The Tsimane life course project has two major goals. The first goal is to conduct basic science on the life course in the context of high disease loads, high work effort, low body mass, and little access to modern medical services. The second goal is test a series of alternative hypotheses, generated by alternative models of the biodemography of aging. The second and third aims will be accomplished through collaboration with project consultants, Ronald Lee and Arthur Robson, and utilizing the facilities, logistical support and research faculty at the Santa Fe Institute, as well as contributions from working group and workshop participants. [unreadable] [unreadable]